Huygens’ principle, in optics, a statement that all points
of a wave front of
light in a vacuum or transparent medium may be regarded as new sources of
wavelets that expand in every direction at a rate depending on their
velocities. Proposed by the Dutch mathematician, physicist, and astronomer, Christiaan
Huygens, in 1690, it is a powerful method for studying various optical
phenomena.

Huygens' principle, although very important, only holds true if there is no rotation, so as long as the outward pressure is uniform. That is why Huygens never explained the formation of colors. Color formation involves rotation and deformation of spherical bodies, so that the geometry moves from radial to bi-lateral, in order for radiation and transverse waves/colors to become visible.